Radio frequency transmitter and method of operating a radio frequency transmitter

Abstract

A radio frequency transmitter comprising an I/Q modulator for obtaining a modulated output signal from an in-phase signal and a quadrature phase signal, and an I/Q modulator control loop controlling said I/Q modulator, characterized by an activation switch capable of activating/deactivating said I/Q modulator control loop. An operating method thereof.

1 . Radio frequency transmitter comprising an I/Q modulator for obtaining a modulated output signal from an in-phase signal and a quadrature phase signal, an I/Q modulator control loop controlling said I/Q modulator, and an activation switch capable of activating/deactivating said I/Q modulator control loop.  
   
   
       2 . The radio frequency transmitter of  claim 1 , further comprising a calibration signal generator which generates an internal calibration signal that can be supplied to said transmitter.  
   
   
       3 . The radio frequency transmitter of  claim 2 , being capable of using a frequency correction burst of an input signal as said calibration signal.  
   
   
       4 . The radio frequency transmitter of  claim 1 , wherein said I/Q modulator control loop comprises an amplitude detector and/or an I/Q correction circuit.  
   
   
       5 . The radio frequency transmitter of  claim 1 , further comprising a digital filter capable of influencing a DC offset voltage of said in-phase signal and/or said quadrature phase signal, and/or capable of influencing a gain of said in-phase signal and/or said quadrature phase signal, and/or capable of influencing a phase difference between said in-phase signal and said quadrature phase signal.  
   
   
       6 . Method of operating a radio frequency transmitter, the radio frequency transmitter comprising an I/Q modulator for obtaining a modulated output signal from an in-phase signal, and comprising a quadrature phase signal, and an I/Q modulator control loop controlling said I/Q modulator, the method comprising the step of activating said I/Q modulator control loop if a suitable calibration signal is supplied to said transmitter.  
   
   
       7 . The method of  claim 6 , further comprising the step of using a frequency correction burst of an input signal as said calibration signal.  
   
   
       8 . The method of  claim 6 , further comprising the step of generating an internal calibration signal.  
   
   
       9 . The method of  claim 6 , in which said calibration signal effects a modulated output signal a complex envelope of which has a constant absolute value.  
   
   
       10 . The method of  claim 6 , in which an I/Q correction circuit controls a digital filter so as to obtain a modulated output signal a complex envelope of which has a constant absolute value, if said calibration signal is supplied to said transmitter.  
   
   
       11 . The method of  claim 6 , in which a calibration signal generator is used for generating an internal calibration signal, in particular if there is an idle time slot which is not transmitted over the air.